“The President has been briefed and we are monitoring the ongoing delays at some airports,” press secretary Sarah Sanders wrote in a statement. “We are in regular contact with officials at the Department of Transportation and the FAA.”

It’s too early to say whether the flight delays at eastern airports will break the shutdown stalemate. But the prospect of a national air travel meltdown has long loomed in the minds of White House and congressional officials as the one thing that might bring an end to the stalemate.

And it comes as Trump is facing increasing pressure from Republicans to find an end to the shutdown, whose consequences have mounted as it stretches longer than a month. On Thursday, Republican lawmakers vented their frustration at Vice President Mike Pence during a tense lunch over a lack of a strategy out of the shutdown.

On Friday morning, air traffic was delayed at two New York-area airports — LaGuardia and Newark — in addition to Philadelphia International Airport due to staffing issues at a Federal Aviation Administration regional air traffic control center.

The delays came as the partial federal government shutdown entered its 35th day and as hundreds of thousands of federal workers missed another paycheck. Earlier in the week the president of a major air traffic controllers union warned that the ongoing shutdown poses a major safety risk.

Administration officials have said as recently as this week that if the shutdown began to devastate air travel, they feared Republicans would jump ship and get on board with a short term Democratic plan to reopen the government.

And it’s not just inside the White House. Outside political advisers to the President and his allies on Capitol Hill have worried major flight issues would amplify the blame Trump is already facing for the shutdown. They, too, believe that major disruptions to air travel would ramp up pressure to reopen the government without wall funding.

Trump’s main foil in the shutdown battle, House Speaker Nancy Pelosi, sought to place blame for the delays on the President.

“The #TrumpShutdown has already pushed hundreds of thousands of Americans to the breaking point. Now it’s pushing our airspace to the breaking point too,” she wrote on Twitter. “@realDonaldTrump, stop endangering the safety, security and well-being of our nation. Re-open government now!”

One of his top allies, meanwhile, suggested the delays could shake loose a deal.

“I think the problems at the airport are a sign of things to come and I’ve been ready for weeks now to reopen the government and give us a chance without a shutdown hanging over us to reach a compromise,” Sen. Lindsey Graham told reporters.

As the shutdown has worn on, Trump and top Cabinet officials have come under scrutiny for appearing to lack empathy for unpaid federal workers. Officials insist the President is concerned about their plight, even if in public he’s made puzzling statements like one he delivered on Thursday suggesting grocery stores might allow regular shoppers to take food without paying.

In conversations with aides, Trump has been focused on two particular areas where Americans might be adversely affected: air travel (including security line waits and delays) and tax returns. He has asked aides whether TSA and FAA workers are breaking laws by calling out sick, likening it to the air traffic controllers strike during the Reagan administration. President Ronald Reagan fired thousands of air traffic controllers in 1981, alleging they broke a law that bans federal employees from going on strike.

When reports first began emerging in early January of higher-than-normal sickouts among TSA agents, the administration sought to downplay the matter, and Trump himself called the notion “fake news” on Twitter.

Yet the issue persisted, and on Friday the TSA said in a statement that call-out rates among officers were double the rate from a year ago.